[Question] the check of ioeventfd collision in kvm_*assign_ioeventfd_idx
Zhenyu Ye
yezhenyu2 at huawei.com
Fri Jul 31 02:39:29 EDT 2020
On 2020/7/31 2:03, Paolo Bonzini wrote:
> Yes, I think it's not needed. Probably the deassign check can be turned into an assertion?
>
> Paolo
>
I think we can do this in the same function, and turnt he check of
p->eventfd into assertion in kvm_deassign_ioeventfd_idx(). Just like:
---8<---
static inline struct _ioeventfd *
get_ioeventfd(struct kvm *kvm, enum kvm_bus bus_idx,
struct kvm_ioeventfd *args)
{
static struct _ioeventfd *_p;
bool wildcard = !(args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH);
list_for_each_entry(_p, &kvm->ioeventfds, list)
if (_p->bus_idx == bus_idx &&
_p->addr == args->addr &&
(!_p->length || !args->len ||
(_p->length == args->len &&
(_p->wildcard || wildcard ||
_p->datamatch == args->datamatch))))
return _p;
return NULL;
}
kvm_deassign_ioeventfd_idx() {
...
p = get_ioeventfd(kvm, bus_idx, args);
if (p) {
assert(p->eventfd == eventfd);
...
}
---8<----
This may be easier to understand (keep the same logic in assign/deassign).
I will send a formal patch soon.
Thanks,
Zhenyu
> Il gio 30 lug 2020, 16:36 Zhenyu Ye <yezhenyu2 at huawei.com <mailto:yezhenyu2 at huawei.com>> ha scritto:
>
> Hi all,
>
> There are checks of ioeventfd collision in both kvm_assign_ioeventfd_idx()
> and kvm_deassign_ioeventfd_idx(), however, with different logic.
>
> In kvm_assign_ioeventfd_idx(), this is done by ioeventfd_check_collision():
> ---8<---
> if (_p->bus_idx == p->bus_idx &&
> _p->addr == p->addr &&
> (!_p->length || !p->length ||
> (_p->length == p->length &&
> (_p->wildcard || p->wildcard ||
> _p->datamatch == p->datamatch))))
> // then we consider the two are the same
> ---8<---
>
> The logic in kvm_deassign_ioeventfd_idx() is as follows:
> ---8<---
> if (p->bus_idx != bus_idx ||
> p->eventfd != eventfd ||
> p->addr != args->addr ||
> p->length != args->len ||
> p->wildcard != wildcard)
> continue;
>
> if (!p->wildcard && p->datamatch != args->datamatch)
> continue;
>
> // then we consider the two are the same
> ---8<---
>
> As we can see, there is extra check of p->eventfd in
>
> (). Why we don't check p->eventfd
> in kvm_assign_ioeventfd_idx()? Or should we delete this in
> kvm_deassign_ioeventfd_idx()?
>
>
> Thanks,
> Zhenyu
>
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